The present invention relates to a thermal recorder employing a linear array of heat producing elements which moves in a direction on heat-sensitive paper advanced in a direction perpendicular to the array moving direction. Particularly, it relates to a thermal recorder for recording groups of information signals successively received at a time interval with different degrees of darkness, by giving to heat-sensitive paper heat energy depending on the amplitude of a received information signal.
The invention can be embodied in a facsimile recorder or in the recorder of an ultrasonic underwater detection system.
Hereinafter, the invention will be explained as embodied in a facsimile recorder for receiving and recording groups of facsimile signals transmitted successively at a time interval from a remote transmitting station, with a group of the facsimile signals recorded on an imaginary scan line on heat-sensitive recording paper.
A prior art facsimile recorder will be explained, with reference to FIGS. 10 and 11. An antenna 101 receives groups of facsimile signals, with a group of the signals including a synchronous signal "S" and signals representing pictures successively received at a time period "Ts" of, for example 1 second, as shown in FIG. 11a. A receiver 102 amplifies and demodulates the received facsimile signals which are coupled to a contact rail 103. An endless belt 104 is extended about a driving pulley 105 and a driven pulley 106, and is driven at uniform speed by a motor 107 through a speed converter 110. Three recording styli 108a, 108b and 108c are fixed on the endless belt at uniform space intervals. Electrically sensitive recording paper 109 moves progressively lengthwise in a direction perpendicular to the direction of stylus scan. The contact rail 103, endless belt 104 and electrically sensitive recording paper 109 are disposed in such a way that both ends of the recording styli slide on the contact rail 103 and the recording paper respectively.
With the prior art facsimile recorder, three styli must be fixed on the endless belt at precisely uniform space intervals, which is very hard to be adjusted, and further, transmitted pictures are not faithfully reproduced, since the degrees of darkness marked on the paper are not in direct proportion to the amplitude of the received facsimile picture signals.